This proposal is for the establishment and study of primary cultures of adipocytes, pre-adipocytes, and fetal hepatocytes derived from obese and lean Zucker rats. The objective is to gain information about the potential for growth and metabolic activity in each of these cell types, which may lead to an understanding of the primary lesion that is involved in hyperplastic obesity. Cells will be derived from tissues excised from obese and lean rats of varying ages, from fetus to mature adult, and placed in culture with growth media supplemented with sera from a variety of sources. Response of cultured cells will be assessed by a variety of microscopic, histochemical, and biochemical methods.